package org.apache.solr.util;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.solr.common.util.NamedList;
import org.apache.solr.common.util.SimpleOrderedMap;

import java.lang.System;
import java.lang.Thread;
import java.util.*;

/**
 * A recursive timer.
 * 
 * RTimers are started automatically when instantiated; subtimers are also
 * started automatically when created.
 * 
 * @since solr 1.3
 * 
 */
public class RTimer {

	public static final int STARTED = 0;
	public static final int STOPPED = 1;
	public static final int PAUSED = 2;

	protected int state;
	protected double startTime;
	protected double time;
	protected double culmTime;
	protected SimpleOrderedMap<RTimer> children;

	public RTimer() {
		time = 0;
		culmTime = 0;
		children = new SimpleOrderedMap<RTimer>();
		startTime = now();
		state = STARTED;
	}

	/**
	 * Get current time
	 * 
	 * May override to implement a different timer (CPU time, etc).
	 */
	protected double now() {
		return System.currentTimeMillis();
	}

	/** Recursively stop timer and sub timers */
	public double stop() {
		assert state == STARTED || state == PAUSED;
		time = culmTime;
		if (state == STARTED)
			time += now() - startTime;
		state = STOPPED;

		for (Map.Entry<String, RTimer> entry : children) {
			RTimer child = entry.getValue();
			if (child.state == STARTED || child.state == PAUSED)
				child.stop();
		}
		return time;
	}

	public void pause() {
		assert state == STARTED;
		culmTime += now() - startTime;
		state = PAUSED;
	}

	public void resume() {
		if (state == STARTED)
			return;
		assert state == PAUSED;
		state = STARTED;
		startTime = now();
	}

	/**
	 * Get total elapsed time for this timer.
	 * 
	 * Timer must be STOPped.
	 */
	public double getTime() {
		assert state == STOPPED;
		return time;
	}

	/**
	 * Create new subtimer with given name
	 * 
	 * Subtimer will be started.
	 */
	public RTimer sub(String desc) {
		RTimer child = children.get(desc);
		if (child == null) {
			child = new RTimer();
			children.add(desc, child);
		}
		return child;
	}

	@Override
	public String toString() {
		return asNamedList().toString();
	}

	public NamedList asNamedList() {
		NamedList<Object> m = new SimpleOrderedMap<Object>();
		m.add("time", time);
		if (children.size() > 0) {
			for (Map.Entry<String, RTimer> entry : children) {
				m.add(entry.getKey(), entry.getValue().asNamedList());
			}
		}
		return m;
	}

	/**
	 * Manipulating this map may have undefined results.
	 */
	public SimpleOrderedMap<RTimer> getChildren() {
		return children;
	}

	/*************** Testing *******/
	public static void main(String[] argv) throws InterruptedException {
		RTimer rt = new RTimer(), subt, st;
		Thread.sleep(100);

		subt = rt.sub("sub1");
		Thread.sleep(50);
		st = subt.sub("sub1.1");
		st.resume();
		Thread.sleep(10);
		st.pause();
		Thread.sleep(50);
		st.resume();
		Thread.sleep(10);
		st.pause();
		subt.stop();
		rt.stop();

		System.out.println(rt.toString());
	}
}
